It really pisses me off when my boyfriend and I go into a restaurant and have a waitress/waiter treat us like crap because she/he figures we're not going to tip well because we're young. Usually, they end up geting a reduced tip simply because we're treated so badly.
I've had the min. wage jobs myself and realize that its hard to be enthusiastic for $5.15/hour. But basic politeness shouldn't be contingent upon a wage. When I go to a fast food place, I don't expect fine table service. But I do expect common curtosey. And that includes more than one napkin dammit!